And the one you posted ("ευτυχία ξεκινά με εσάς") is erroneous, because:1. Nouns can't be used alone without an article in the beginning of the sentence. So, you should add the article of the noun "ευτυχία" in front of it. (The word "ευτυχία" is feminine, so its article is certainly "η")2. The verb "ξεκινάω/ξεκινώ" means that one starts something [ξεκινά(ει) is the third person singular form of this verb]. If you wanted to mean "to begin", "αρχίζω" (αρχίζει is the third person singular form of this verb) would be the correct verb for you to use in this sentence.3. "με (ε)σάς" is very formal in this sentence. Since your sentence seems like an informal sentence, "με (ε)σένα" fits better to this sentence.